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Biomedical subjects

R S Labow

Publications and source records attributed to R S Labow.

At least 73 records · Page 4Linked to original sources
PubMed1986

Contamination of platelet storage bags by phthalate esters.

Phthalate esters are the most extensively used plasticizers in the manufacture of polyvinylchloride (PVC) plastic. Many medical devices used in the collection and storage of blood components are made of PVC plastic containing di(2-ethylhexyl) phthalate (DEHP). DEHP leaches at a rate of 100 micrograms/ml X d into platelet concentrate (PC) supernatant when PCs are stored in PVC containers. It is only possible to store PCs for 72 h in this DEHP plastic, after which time the platelet function has deteriorated and they cannot be used for transfusion therapy. Since it was desirable to find a container that permitted longer storage times and because of the concern for the toxicity of DEHP, new bags, manufactured with different plastic formulations without this plasticizer, were tested for PC storage. Using these new containers, such as the PL732 [polyolefin (PO) plastic], and the CLX300 and PL1240 [tri(2-ethylhexyl) trimellitate (TEHTM) PVC plastic], it was possible to store PCs for 5 d while preserving platelet function. In spite of these new plastic bags being manufactured without DEHP, we found DEHP and its metabolite mono(2-ethylhexyl) phthalate (MEHP) as contaminants of the supernatant of the PCs stored in these containers. After analyzing the plastic material of each of these containers, we were able to identify the source of the contamination as coming from the plastic materials that were used in the manufacture of the bags. The sterilization process of the PL732 bag was investigated, since it was found that when the plastic of the PL732 bag was analyzed prior to sterilization, no contamination by DEHP was detected; however, whether the PL732 bag was sterilized together with the primary PVC bag or separately, using ethylene oxide, contamination by DEHP was found, suggesting contamination of the sterilization unit by DEHP.

Blood Platelets↗
PubMed1986

Distribution of di(2-ethylhexyl) phthalate and products in blood and blood components.

In order to impart flexibility, plastic medical devices incorporate liquid plasticizers into their structure. Data from several laboratories, including ours, have shown that these compounds leach from blood bags and tubing during collection of blood, storage of various blood components and during kidney dialysis and cell and plasma apheresis procedures. After the plasticizer di(2-ethylhexyl) phthalate leaches from poly(vinyl chloride) blood packs, it is converted by a plasma enzyme to a more toxic metabolite, mono(2-ethylhexyl) phthalate. Blood fractionation products from outdated plasma contain mono(2-ethylhexyl) phthalate, the highest level being found in normal serum albumin. Recently, we have reported that di(2-ethylhexyl) phthalate actually binds to the red blood cell membrane and reduces its osmotic fragility. Current methods of red cells storage, which permit utilization up to 35 days after collection, are not possible without this membrane stabilization. Platelets are now stored for 5 days in the Fenwal PL 732 polyolefin bag. Although stated to be essentially free of liquid plasticizers, a significant level of leaching from this bag into the extracts of stored platelet concentrates was observed.

Blood Platelets↗
PubMed1984

A comparison of four sulfhydryl cathepsins (B, C, H, and L) from porcine spleen.

Four sulfhydryl cathepsins, B, C (dipeptidyl aminopeptidase I), H, and L were isolated from porcine spleen. They are all glycoproteins of similar amino acid compositions, which are comparable with those of cathepsins B and H from other sources and so with papain. All four cathepsins exist in multiple charged forms: B, C, H, and L have isoelectric points in the range 4.3-5.4, 5.3 and 5.9, 5.2-5.7, and 7-8.7, respectively. The molecular weights of cathepsins B and H were 24 000 and 26 000. Anomalous behaviour of cathepsin L on both conventional gel filtration and high pressure liquid chromatography precluded a precise assessment of its weight which is between 22 000 and 28 000. The isolated mercurial derivative of cathepsin C has a molecular weight of 56 000 (an active dimer formed on reduction). Cathepsins B and H also aggregate.

Animals↗
PubMed1983

Porcine cholesterol esterase, a multiform enzyme.

Cholesterol esterase (sterol-ester acylhydrolase, EC 3.1.1.13) has been purified from porcine pancreas by two methods, one of which was previously reported by Momsen, W.E. and Brockman, H.L. (Biochim. Biophys. Acta. 486 (1977) 102-113). Multiple forms of the enzyme were demonstrated throughout the course of both purification procedures. These forms hydrolyzed both p-nitrophenyl acetate as well as cholesteryl oleate. Isoelectric focusing was used to select one form of cholesterol esterase having a pI of 4.3 for further study. Using high-pressure liquid chromatography on a TSK Spherogel column this apparently homogeneous preparation of cholesterol esterase was separated into two components having molecular weights equal to 90 000 (peak I) and 45 000 (peak II). The number of each amino acid residue in peak I was double that of the corresponding residue in peak II, suggesting a dimer-monomer relationship. The N-terminal analyses showed that the first five amino acid residues were the same in peak I and peak II. The enzyme is a glycoprotein containing glucosamine, glucose, galactose, mannose and rhamnose; it is inhibited by diisopropyl fluorophosphate.

Amino Acid Sequence↗
PubMed1982

Brain glucocerebrosidase in Gaucher's disease.

Using glucocerebroside labeled with carbon 14 as the substrate, we determined that homogenates of brain tissue from both neuropathic and nonneuropathic cases of Gaucher's disease were profoundly deficient (more than 85%) in glucocerebrosidase activity. The beta-glucosidase activity, as measured with 4-methylumbelliferyl-beta-D-glucopyranoside as the substrate, in the homogenates of brain from four cases of Gaucher's disease was less sensitive to inhibition by conduritol B epoxide (CBE) when compared with normal brain beta-glucosidase. However, when homogenates were assayed with radiolabeled glucocerebroside as the substrate, no differential sensitivity toward CBE was indicated, suggesting the presence of an additional, CBE-insensitive, beta-glucosidase in brain tissue. Residual glucocerebrosidase activity partially purified from the brain of an adult with type 1 Gaucher's disease was activated threefold by gluconoyl hydrazine, whereas the same enzyme from control brain was unaffected, and eight times less sensitive to gluconolactone inhibition.

Adult↗
PubMed1981

Purification and characterization of a cytosolic broad specificity beta-glucosidase from human liver.

A cytoplasmic beta-glucosidase has been isolated and purified 9,000-fold to homogeneity from the liver of a case of type 1 Gaucher's disease to a specific activity of 400,000 nmol/h/mg of protein. Although markedly elevated above control levels in this case of adult Gaucher's disease, the activity of this cytosolic liver enzyme was found to be markedly deficient in two cases of neurologic Gaucher's disease. The purification scheme employs QAE-Sephadex, DE52 cellulose, CM-Sephadex, hydroxylapatite, and Cibacron blue-Sepharose chromatography, and preparative isoelectric focusing. The beta-glucosidase preparations isolated from the liver of the case of adult Gaucher's disease and control liver have similar physical properties. Both enzymes have a molecular weight of approximately 53,000, sw,20 of 4.3, pI of 4.5-4.6, a pH optimum between 5 and 6, and a high affinity for 4-methylumbelliferyl-beta-D-glucopyranoside (Km = 0.06-0.07 mM). The enzymes from both sources also have a broad specificity and will hydrolyze the 4-methylumbelliferyl derivatives of beta-D-galactose, beta-D-fucose, beta-D-xylose, and alpha-L-arabinose in addition to several aryl-galactosides and steroid-glucosides. The cytoplasmic beta-glucosidase will not hydrolyze glucocerebroside and shows no cross-reactivity with antibodies prepared against lysosomal glucocerebrosidase. Both cytoplasmic beta-glucosidase and glucocerebrosidase will hydrolyze 17 beta-estradiol-17'-beta-D-glucose, and the activity of both enzymes on this substrate is increased more than 15-fold in the presence of the Gaucher spleen heat-stable factor. The role of this cytoplasmic beta-glucosidase in the etiology of Gaucher's disease and its possible relationship to lysosomal glucocerebrosidase are discussed.

Cytosol↗
PubMed1980

Estrone beta-glucosidase activity in human placenta.

The 105 000g supernatant from human placental homogenates, prepared in the presence of sodium taurocholate and Cutscum, contained beta-glucosidase activity towards estrone glucoside as well as towards 4-methylumbelliferyl glucoside (4-MU-glucoside) and glucocerebroside. After partial purification, the estrone glucosidase was found to be active only after the addition of negatively charged phospholipid, whereas the other beta-glucosidases did not exhibit this requirement. The estrone glucosidase was separated from the 4-MU-glucosidase by chromatography on Sephadex G-200 with 0.1% sodium taurocholate in the eluting buffer. The estrone glucosidase was mainly contained in material with a pI of 4.7, while the 4-MU-glucosidase was distributed in fractions with pI values of 4.7 and 6.2 to 6.4. The partially purified estrone glucosidase had a pH optimum of 5.8, as distinct from that of 6.4 found for the 4-MU-glucosidase, and differed markedly from the 4-MU-glucosidase in its response to treatment with heat, sulfhydryl reagents, and detergents. Its sensitivity to changes in pH differed from those reported for glucocerebrosidase.

Detergents↗
PubMed1976

Transfer of xylose to steroids by rabbit liver microsomes.

Rabbit liver microsomal preparations can transfer xylose from UDP-xylose to estron, 17alpha-estradiol, and 17beta-estradiol, and, in poorer yield, to diethylstilbestrol and p-nitrophenol. No transfer of xylose to estriol, testosterone, epitestosterone or 17alpha-estradiol 3-glucuronide could be demonstrated. The xyloside of [6,7-3H]estrone which was formed by liver microsomes crystallized to constant specific activity with estrone beta-D-xylopyranoside, the chemical preparation of which is described.

Animals↗
PubMed1975

The transfer of glucose to steroids by chimpanzee liver microsomes.

Microsomal preparations from chimpanzee liver can transfer glucose from UDPglucose to the 17alpha-hydroxyl group of 17alpha-estradiol and of 17alpha-estradiol-3-glucuronide. A phenolic glucoside of estrone, but not of either 17alpha- or 17beta-estradiol is also formed. No formation of glucosides of p-nitrophenol, or of diethylstilbestrol was demonstrated. The specificity of glucosyl transfer in the chimpanzee is not identical to that in either the human, the rabbit, or the sheep.

Animals↗
PubMed1974

A comparison of glucoside formation by liver preparations from the rabbit and the mouse.

Liver homogenates from mice and from rabbits transfer glucose from UDP-[6-(3)H]glucose, at pH7.0, to oestradiol-17alpha, oestradiol-17beta, oestradiol-17alpha 3-glucuronide, p-nitrophenol and diethylstilboestrol. In the rabbit the phenolic steroids were better substrates than p-nitrophenol for the glucosyltransferase, whereas the reverse was true in the mouse. At pH8.0, rabbit liver, but not mouse liver, transferred glucose to oestradiol-17alpha 3-glucuronide in better yield than that at pH7.0. Evidence is presented for the presence of two glucosyltransferases in rabbit liver. One of these has a pH optimum at about 8.0, and is highly specific for oestradiol-17alpha 3-glucuronide, whereas the other, which has a pH optimum at about 7.0, is similar in this respect to the transferase in mouse liver.

Animals↗
PubMed1972

The formation of glucosides of isoflavones and of some other phenols by rabbit liver microsomal fractions.

1. Rabbit liver microsomal fractions in vitro effected the transfer of glucuronic acid from UDP-glucuronic acid to biochanin A, formononetin, daidzein, genistein and equol. Only monoglucuronides were formed. 2. The same isoflavones were converted into monoglucosides when UDP-[6-(3)H]glucose was substituted for UDP-glucuronic acid in the incubation medium in vitro. The glucosides were formed in much lesser yield than were the glucuronides. 3. The glucoside of genistein was identified as genistin (genistein 7-glucoside) by Sephadex chromatography and reverse isotope dilution. 4. The specificity of the glucuronyl- and glucosyl-transfer mechanisms was compared for a series of steroids and other phenols in addition to the isoflavones. It was concluded that separate transferases were responsible for the formation of the two types of glycosides.

Animals↗